easy to find
where: gardens, side walk strips, yards, rivers (and other water bodies)
sold in bulk
usaully appears in groups,
in fact this is more of a general descriptor used in landscapping
you also probably can’t buy a single river rock
you could probably get away with calling any rounded plain rock “river rock”
but then you wouldn’t have the same assurance that it was quaried from a real body of water (or dried river bed).
uses:
groundcover
pathways
borders
decoration
weed supression
moisture retention
french drains
drainage
concrete
cobble stone